The Mishna (32b) tells of a group of people walking together who spy a figure walking towards them:
- One person says: I will be a nazir if that is So-and-so approaching us.
- The second one says: I will be a nazir if it is not So-and-so.
- The third says: I will be a nazir if one of you is a nazir.
- The fourth says: I will be a nazir if you are both nezirim.
- The fifth says: I will be a nazir if all of you are nezirim.
Beit Shammai rules that all of these people are nezirim, based on his position which appears in the first Mishna in the perek (see 30b–31a) that even a mistaken nezirut takes effect. Beit Hillel says that only those whose conditions were not fulfilled become nezirim.
Beit Hillel’s statement is obviously problematic – clearly those people whose conditions were not fulfilled should not become nezirim – and Rav Yehuda suggests amending the Mishna to read that only those whose conditions were fulfilled should become nezirim. Abayye has another suggestion to explain Beit Hillel. He suggests that there is an additional statement attached to the original one, and the person added ee nami lav ploni hu – that also if it were not the person, he would become a nazir. Thus, the statement of Beit Hillel means that if the original condition was not fulfilled he will become a nazir, assuming that the second condition is fulfilled.
Rashi explains this to mean simply that the person says, “I will be a nazir if that is So-and-so approaching us, and also if it is not So-and-so I will be a nazir.” The other rishonim point out that this obvious ruling hardly needs to be taught by the Mishna.
The Me’iri suggests that the case is more complicated. When a man says, “I will be a nazir if the man approaching us is Reuven and not Shimon,” and then it turns out that it was another person entirely, although his primary statement was not fulfilled (it was not Reuven) since his secondary statement was fulfilled (it was not Shimon) he becomes a nazir.